Continued loading from forecast new snow and wind will trend the avalanche danger up over the weekend.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain on Sunday
Weather Forecast
Moderate southwest winds and 5-10 cm overnight for Saturday morning. Moderate southwest wind and 15-25 cm during the day Saturday. Another 15-25 cm by Sunday morning. Winds becoming light west-southwest during the day as the storm moves east and leaves another 5-8 cm. Monday should be light winds and light snow. The freezing level should remain at about 500 metres throughout the forecast period with a chance of a brief rise to around 800 metres on Sunday morning.
Avalanche Summary
Widespread loose dry activity up to size 1.5 and explosives control up to size 2.0 has been reported from Whistler Friday morning. I suspect that some pockets of wind transported snow may be easy to trigger on lee aspects. Watch for longer fracture propagations resulting in larger avalanches as the new storm snow load increases and settles into a cohesive slab.
Snowpack Summary
New storm snow was reported to be releasing very easily as loose dry above the old surface, and may be sitting on a new surface hoar layer buried on December 17th. The new snow came in a bit warmer at about -3 on top of the previous thin layer of cold snow at about -11 on Thursday, resulting in some surface slabbing and long propagations. Northerly winds transported some snow on Wednesday into soft wind slabs on lee aspects. There were some reports of easy test results between the wind slab and the old storm snow below. These new wind slabs overlie 40-50cm of storm snow from last weekend.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.